This invention relates to a valve for providing fluid communication between the interior of a tubing string in an oil well and the well annulus surrounding the tubular string. More particularly, the apparatus relates to a circulation valve for use in a testing program for a submerged oil well.
Circulation valves are known for use in a testing program in an oil well wherein the circulation valve opens after a predetermined number of incremental movements. These incremental movements are caused by an increase in annulus pressure wherein the annulus pressure is exerted against a piston to compress an inert gas in the apparatus for supplying a return spring force.
Such a circulation valve is disclosed in U.S. Pat. No. 3,850,250 issued Nov. 26, 1974 to Holden et al. and assigned to the assignee of the present invention.
Other valves for use in an oil well are known wherein the valves are operated by changing the pressure differential between the pressure in the annulus of the well and that pressure present in a flow channel in the interior of the tubing string.
The use of a compressible liquid to provide spring force for use in industrial applications is also known.
Disclosed is an oil well apparatus having a circulation valve section for moving from a closed condition to an open condition after a set number of incremental movements. The apparatus includes an outer tubular housing and an inner slidable power mandrel assembly with a power piston between the outer housing and the power mandrel assembly. Well annulus pressure is communicated to one side of the power piston and a compressible liquid is communicated from a spring chamber to the other side of the power piston.
As the apparatus is lowered into the well bore, the volume of the compressible liquid may change in response to changes in the pressure and temperature in the well bore. A ratchet mechanism is provided in one embodiment for allowing the power mandrel assembly to move in a first direction as the compressible liquid expands without moving the circulation valve section provided in the tool. When the testing depth is reached, an operating power pressure increase may be added to the well bore to move the power mandrel assembly in a second opposite direction for causing the operating mechanism of the circulation valve section to operate.
In a second embodiment, a ratchet arrangement is provided which allows the volume of the compressible liquid to either expand or contract as the tool is lowered and raised in the well bore. A ratchet assembly is provided which only transmits motion in a limited area for providing operating strokes from the power mandrel assembly to the circulation valve section. When the ratchet mechanism of the assembly is on either side of this limited area, the ratchet allows relative motion between the ratchet assembly and the power mandrel assembly thereby allowing the compressible liquid to expand or contract. The ratchet assembly transmits power strokes when the ratchet assembly is in the limited area thereby transmitting incremental movement to the circulation valve section during pressure increases exerted on the well annulus.
The disclosed circulation valve section includes a holding ratchet and a pull ratchet assembly. During pulling strokes the pull ratchet assembly pulls the circulation valve section toward the open position, and the holding ratchet assembly ratchets to allow the pulling motion. When the increased annulus pressure is released, the holding ratchet assembly holds the circulation valve section operating mechanism, and the pull ratchet assembly ratchets to allow the power mandrel assembly to obtain another bite on the operating mechanism. Thus, the circulation valve section is incrementally moved toward the open position. A reciprocating allowing means is provided in both embodiments of the first mentioned ratchet to allow reciprocating motion to be transferred from the power mandrel assembly to the pull ratchet and hold ratchet assemblies of the circulation valve section operating mechanism.
A compressible liquid such as silicon oil is used to supply spring force in the disclosed apparatus. This compressible liquid may change volumes as the apparatus is lowered into the well bore, but is completely pressure balanced such that a pressure difference does not exist between the liquid spring chamber in the tool and the annulus pressure in the well annulus outside of the tubular housing. Once the testing depth is reached, power pressure increases may be applied to the fluid in the well annulus to compress the compressible liquid in the liquid spring chamber in the apparatus. The pressure increases will cause the compressible liquid to compress and will supply operating strokes to be transferred to the circulation valve section. When the well annulus pressure increases are removed, the compressible liquid will once more expand to supply a returning spring force to the operating mechanism of the circulation valve section.